One-pot synthesis of new liquid crystalline indeno heterocyclic materials

Disulfur dichloride converts 1-(dicyanomethylene)indane 3 into the methylen eindene 4 and the red indeno-1,2-thiazine 5; it also converts inden-3-ylace tic acid 7 into methyleneindenes 8 and 9, dithiolone 10 and the deep purple thiophenone 11; upon melting crystals of 4 and 11 are strongly birefringen t and 5 exhibits thermochromicity; mechanisms are outlined for the novel tr ansformations and X-ray crystal structures for 5 and 10 are analysed.